Mercury switch



Dec. 19, 1944. M. w. GRIFFES 2,365,634

MERCURY SWITCH Filed May 21, 1942 .v 2 Sheefs-Sheet 1 A lag 4144 .445

INVENTOR. H usrorv (Al- GmFr-eo,

@a igw Dec. 19, 1944. v w GRlFFEs 2,365,634

. MERCURY SWITCH Filed May 21, 1-942 2 Sheets-Sheet 2 INVENTOR. MILTONW. GRIFFES' Patented Dec. 19, 1944 UNITED, STATES PATENT OFFICE MERCURYSWITCH Milton W. Grifles, Cleveland, Ohio, assignor to The ElectricController & Manufacturing Company, Cleveland, Ohio, a corporation ofOhio Application May 21, 1942, Serial No. 443,848

1'7 Claims.

This invention relates to mercury flow switches, and more particularlyto mercury switches in which the mercury is caused to flow bygravity orother means and which provides a variable time delay either in theopening or in the closing of a circuit through the switch.

Heretofore, the .time required to operate hermetically sealed, gravityoperated mercury switches of the tubular type has been varied byadjustment of the initial inclination of the longitudinal axis of theswitch. By means of such adjustment the rate of flow of mercury throughan orifice of definite size was controlled by variations in the pressurehead due to the angle of inclination of the axis of the tube.

In many installations, however, it is either undesirable to vary theangle of initial inclination of the switch, or, due to the small totalangle through which the switch is tilted for operation, impossible to doso and obtain a satisfactory range of time adjustment for most purposes.For example, it is desirable to control the successive operation ofelectromagnetic contactors by time delay mercury switches drivendirectly by the. contactor shafts.

I Since the total angle of rotation of such shafts is seldom greaterthan ten degrees, it is apparent that possible adjustments of theinitial inclination of the switch cannot provide either a wide range oraccuracy of time variation. I

In accordance with this invention, two means are provided which may beused singly or in combination to effect variations of the time delayperiod of a hermetically sealed, tubular mercury switch depending uponth axially rotated position of the switch. One of the two meanscomprises a valvular septum containing a plurality of different sizedorifices spaced apart near its periphery, and mounted trans-axialLv ofthe tube which forms the switch body'so as to divide the tube into twochambers. By adjustment of the axial rotated position of the tube, theorifice, or orifices of the desired size can be disposed lowermost. Therate of flow of mercury from the first j chamber into the second chamberthrough the valvular septum depends upon thesize of theor the septumtherein, is 'rotated about its longitudinal axis. The range of timeadjustment available bypre-selection of .oriflce size alone is somewhatlimited in switches of small diameter since, due to the inability ofmercury to how through extremely small openings, only a limited numberof different sized orifices can be utilized.

The other of the two means by which the time adjustment of a switch isaffected is by Dre-selection, by adjustment of the axial rotatedposition of the tube, of the amount of mercury which must flow throughthe septum in order to open or close a. circuit through the switch. Inone embodiment of the invention, said other means comprises a chamberinto which the mercury flows through an orifice in the septum, thechamber being defined by the septum and an annular shaped piece ofrefractory material, hereinafter referred to as a breaker, whichismounted obliquely with re;- spect to the longitudinal axis of thetube. i

A change in the axial rotated position of the switch effects a change inthe amount or volume of mercury which must flow through an orificebefore the switch operates, even though the oriflees in the septum areof the same size. The "effective volume 'of the receiving chamber istherefore adjustable, and effective volume," as hereinafter used, meansthat volume of a mercury switch chamber which must be filled by themercury or from which the mercury must flow before operation of theswitch, so that the level of the surface of the mercury is suflicient tomake or break contact. Likewise, "effective volume of mercury" is thevolume of the mercury which must flow through an orifice to effectoperation of the switch.

The principal object of this invention is to provide a new and improvedtime delay mercury switch.

Another object is to provide a gravity operated, hermetically sealedmercury switch having a time delay period in opening or closing that isboth accurate andadjustable throughout a wide range.

Another object is to provide a tubular mercury switch having theduration of a time delay period in opening or closing predetermined byselection of the axial rotated position of the switch.

Still another object is to provide a gravityoper ated, hermeticallysealed, tubular mercury switch having a valve mechanism which regulatesthe rate of flow of mercury within the switch in accordance with theaxial rotated position of the switch. s

A specific object of this invention is to provide a tubular mercuryswitch having a transaxial septum pierced by an orifice means which iseccentric with respect to the axis of the septum and of which differentportions, circumferentially with respect to said axis, are of difierenteiiective area with respect to each other, any portion of which may beselected, by rotation of the switch about its axis, to serve as apassage for the mercury during the timing period of the switch.

Another object is to provide a two chamber tubular mercury switch havingthe effective volume of one of the chambers variable consequent uponaxial rotation of the tube.

A further specific object is to provide a tubular mercury switch havingtwo chambers separated by a transaxial septum containing a plurality ofdifierent size orifices one or more of which may be selected for use byaxial rotation of the switch and in which the efi'ective volume of oneof the chambers is variable consequent upon the same axial rotation ofthe switch.

Another object is to provide a valve mechanism for a mercury switchwhich permits retarded flow of mercury therethrough in one direction andwhich flexes to permit unretarded flow of mercury in the otherdirection.

Still another object is to provide a hermetically sealed mercury switchhaving an adjustable time manufacture by relative positioning ofstandard parts.

Other objects and advantages will become apparent from thefollowingspecification wherein reference is made to the drawings, inwhich Fig. 1 is a longitudinal sectional assembly View showing apreferred switch for closing a circuit after a time delayandillustrating the prising, as shown, a rigid support l6 and a flexibleseptum 24. Said mechanism may be secured in the tube by cementing andwelding the support IE to the shoulder i4 and the adjacent counterboresurface. A circular supporting clamp 5 for the tube in has a projectingbracket 6 attached, as by a pin 8, to a bracket 1. The latter may be apart of an electromagnetic contactor arm. A bolt and wing nut assembly'9 of the clamp 5 permits the tube to be adjustably secured in differentrotated positions about its longitudinal axis.

The support 16 is preferably. a spider frame Figs. 3 and 4) having a-rim portion 18 including a flange il, a hub l9, and spokes 20. Theseptum 24 is a fiat circular disc of flexible material, such asrubberfattached at its center to the hub l9 as by a bolt 26 and a nut28. A thin washer 29 spaces apart the septum 24 and its support. Thediameter of the septum 24 should be slightly less (e. g. inch) than theinternal diameter of the closed end of the tube 10.

The septum 24 divides the tube l0 into two chambers 32 and 34. When thetube i0 is tilted to its normal position (Fig. 1) any mercury then inthe chamber 34 deflects the flexible septum 24, and fiows quickly aroundthe periphery of the septum into the chamber 32. The marginal area ofthe septum 24 is forced by'pressure of the mercuryin the chamber 32 tomake a tight seal with the rim i8, thus preventing return flow switch inone of its axial rotated positions and tilted to its normal inoperativeposition:

Fig. 2 is alongitudinal sectional view of the.

switch of Fig. 1, partly in elevation and showing the switch tilted toits timing position;

Fig. 3 is an enlarged cross sectional view of the switch and is takenalong the line 3-3 of Fig. l and shows the valve mechanism;

Fig- 4 is an enlarged central sectional subassembly view of the valveand its supporting Fig. 9' is a sectional view along the line 9-9 ofFig. 8 as viewed from the left, showing the breaker and terminalarrangement;

Fig. 10 is a view similar to Fig. 9 with the switch rotated 180 degrees.Referring to Figs. l'and'2, the body of the switch comprises a-metaltube l0 closed-at one end by an integral wall II and open at the otherend 12. The open end portion is preferably enlarged in diameter, as bycounterboring to somewhat less than half the length of the tube, thusforming an annular shoulder H. The shoulder positions a suitable valvemechanism If: comorifice means may be considered to comprise anelongated circumferential slot of decrescent radial width in which casethe area of the orifice means within any given sector is or would be ofdifferent efiective size from the area within an equal but angularlydisplaced sector. For practical purposes, a circumferential series ofopen-.- ings of progressively decrescent size. form, in effect, such aslot and do not materially weaken the septum. Such openings 30a, 30b,30c and 30d, as shown by Fig. 3, are of increasing area in the ordernamed and circumferentially spaced along slightly more than. one-half ofthe periphery of the septum 24, permitting the flow of mercury from thechamber 32 into the chamber 34.

By rotating the septum 24 about its axis, orifice means of selectedsizes may be positioned at the lowermost portion of the tube thereby tocontrol the rate of return of the mercury therethrough into the chamber34. Rotation of the septum, in the illustrative example, is accomplishedmerely by rotating the tube about the septum axis.

I The open end I 2 of the tube I0 may be closed by a thimble shapedpiece of insulation 36 secured to and surrounding a terminal 38, theinner end of which is beveled to form an oblique face 39. The outer endof the terminal rests tightly against the closed end of the thimble 36aseaese the oblique position of the-breaker shown. The breaker issecured, as by cement, to the inner end faces of the thirnble 36 and to.the inner wall of the tube i0. As shown in Figs. 1 and 2, the breaker 42and the oblique face 39 of the terminal 38 may be parallel with eachother and spaced apart a short distance to permit a stationary pool- 4|of mercury to be retained therebetween. Although the oblique face 39 ofthe terminal 38 and the face of the breaker '42 are shown to beplanular, it is obvious that they could be curved surfaces as well. Forexample, a logarithmic :onfiguration of these faces causes theadjustnent of the switch to be logarithmic in nature.-

A suitable gastight seal is made between the tube I and the thimble 36and the ends of the tube ID are spun over as at to secure the thimble 36is place. Before the tube It! is sealed, a uantity of mercury is placedtherein and the ;ube i0 is either evacuated or evacuated and filled i.

at super-atmospheric pressure with a suitable ionization resisting gassuch as hydrogen or neon as is common in the art. It is desirable thatthe quantity of mercury in the switch be greatly in excess of the amountrequired to provide a circuit between the terminal 38 and the tube i0.

- For simplicity andeconomy, one terminal of the switch may be formed bythe tube Ill to which a flexible conductor 48 may be attached, and theother terminal 38 may be connected to a flexible conductor as by fittingthe end of the conductor 50 into a hole drilledthrough the base of thethimble 36 and into the terminal 38.

When the switch is in the position shown in Fig. 1 a main body 43 ofmercury is in the chamber 32 and its surface is below the lowermostportion of the orifice means in the septum 24.

When the left end of the tube I0 is raised approximately ten degrees tothe position shown in Fig. 2, some of the mercury of the body 43 in thechamber 32 flows into the chamber 34 through the lowermost portion ofthe orifice means which, in the illustrative example, is the orifice 30din the septum 24. Although when the tube H1 is first moved to theposition of Fig. 2 more than 'one orifice in the septum 24 may be belowthe surface of the mercury 43, mercury generally flows only through thelowermost orifice because the fluid characteristics of mercury are suchthat considerable pressure head is required to cause it to fiow throughsmall openings. If the mercury does flow through more than one orificein a given position of the switch, the time delay period ispredetermined because of the sizes of the orifices and their respectivedepths below the surface are preselected. Due to that phenomenon ofmercury flow, the series of orifices provides a substantially uniformlyincreased or decreased fiow for changes in rotated position, about thesame inefiect as a continuous slot of uniformly decrescent width fromone end to the other. When sufficient mercury is in the chamber 34 tooverflow through the opening 31 in the breaker .42, electrical contactis made with the pool 4| of mercury retained between the breaker 42 andthe terminal 38. a 7

If the axial rotated position of the tube H1 is such that the portion ofthe breaker 42 closest to the septum 24 is lowermost during'the timingoperation, the effective volume of the receiving chamber 34 is aminimum, and only a relatively small quantity of mercury need pass fromthe chamber 32 into the chamber 34 before it overflows through theopening 31 and makes contact with the mercury pool 4|.

If the tube i0 is rotated 180 degrees so that the portion of the breaker42 farthest from the septum 24 is lowermost, the effective volume of thereceiving chamber .34 is a maximum and a large amount of mercury mustflow into the chamber 34 before it overflows through the opening 31.Rotation of the tube to intermediate positions changes the effectivevolume of the receiving chamberdepending upon the axial rotated positionselected.

Thus timing may be adjusthed upon rotation of the tube ill by either oftwo means, one being the rotated position of the orifice means and theother being the rotated position of chamber 34. By combining the two, asin the present example, a much wider range can be obtained than witheither-alone. As shown in Figs. 1, 2 and 3, the septum 24 and thethlmble 36 have been so mounted in the tube ID that when the tube I0 isrotated to a given zero position, the orifice 30d, which is the largestof the orifices in the septum 24, is at the bottom of the tube Ill andthe portion of. the breaker 42 closest to the septum. 24 is also at thebottom of the tube 0. Under these conditions the rate of the flow ofmercury through the orifice 30d is a maximum, and the total amount ofmercury which mustflow to cause operation of the switch is a. minimum.Therefore, the time delay interval of the switch is a minimum. If thetube I0 is rotated 180 degrees about its longitudinal axis, the smallestorifice 30a is at the bottom and the portion of the breaker 42 farthestfrom the septum 24 is lowermost. Under those conditions, the time delayperiod of the switch is a maximum since the largest amount of mercurymust fiow from the chamber 32 through the smallest orifice 30a beforethe circuit through the switch is completed.

It is obvious that if the switch is rotated to positions intermediatethe zero position and the degree position, intermediate values of timedelay are obtainable. 0n the other hand, if a'wide angle of rotation fora slight increment of adiustment is desired, the septum 24 can beinstalled in a rotated position such that the largest effective volumeof the chamber 34 and the largest portion of the orifice meanscooperate.

Switches providing various limits of time ranges and timing periods maybe constructed merely by altering the distance between the valvemechanism l5 and the thimble 36, as by changing the depth of thecounterbore which forms the shoulder 4. The adjustment possible by sodetermining the position of the shoulder is limited however by theobvious relationship between the actual volume of the chamber 32, thequantity of mercury in the switch, and the various effective volumes ofthe chamber 34.

In order to interrupt the circuit through the switch the tube I0 istilted back to the position of Fig. l. whereupon substantially all ofthe mercury in the chamber 34 flows into the chamber 32 in an extremelyshort time as previously described.

A modified form of septum which may be substituted for the septum 24 isshown at 52 in Fig. 6, and has a plurality of equal sized orifices 54a,54b, 54c, 54d and 54e uniformly spaced about one half of its periphery.When the septum 52 is substituted for the septum 24, the adjustment ofthe time delay of the switch is due only to the variation in theeffective volume of the receiving chamber 34 consequent upon adjustmentof the axial rotated position of the tube in, and is not due to adifference in the rate of fiow'of the mercury through an orifice.

A' septum 56 shown in Fig. 7 is also similar to the septum 24 and may besubstituted therefor.

In switches of small size the number of orifices which may be placednear the periphery of onehalf of the septum'is limited, and, therefore,the

.range of time adjustment may not be as great as desired for someapplications. The septum 56 has orifices 58a, 58b, 58c, 58d and 58ecircumferenriphery and having sizes intermediate those of adjacentorifices 58a, 58b, 58c, 58d and 58e. When the septum 56 is used in placeof the septum 24, almost twice as many steps of time adjustment arerendered available due to the fact that the time delay adjustmenteffected by the oblique face 39 of the terminal 38 and the obliquelymounted breaker 42 is not dependent upon the unidirectional axialrotation of the tube H] from the position shown in Fig. 1.

The switch of Fig. 5 is the same as that of Fig. 1 and Fig. 2 but isassembled to provide a time delay period in the opening of an electriccircuit. This reverse timing operation is obtained by mounting theseptum 24 on the right instead of the left side of the support H5. Thereversal of the position of the septum 24 causes the controlled fiow ofmercury from the chamber 34 into the chamber 32 to be retarded andpermits the flow of mercury from the chamber 32 into the chamber 34 tobe unimpeded. If the axial rotated position of the tube III is such thatthe chamber 34 has its largest effective volume and the tube I is in thehorizontal position, along time is required for sufiicient mercury toflow from the chamber 34 into the chamber 32 to result in interruptionof ,the circuit between the tube l0 and the terminal 38. Rotation of thetube ll! of the switch of Fig. 5 about its longitudinal axis changes theeffective volume of the chamber 34 as before so that a differentpredetermined amount of mercury must flow from the chamber 34 tocause'opening ofthe circuit through the switch. The switch of Fig. 5 isreset by raising the closed end ll of the tube In about ten degreeswhich causes a. rapid flow of mercury from the chamber 32.into thechamber 34 around the periphery of the deflected septum 24.

The modified septa shown in Figs. 6 and 7 may be substituted for theseptum 24 shown in Fig. 5. The inside diameter of the annular flange I1is the same as the inside diameter of the closed end of the tube Ill andtherefore a septum of the same diameter can be used for both thenormally open and the normally closed types of switches. I

The oblique disposition of the breaker and terminal face may be obviatedby a construction such as shown in Figs. 8, 9 and 10. As thereillustrated, a right angled cylindrical block 6| of insulatingmater'i'ial is sealed in the open end l2 of .a tube 60, which is similarto the tube I0 except that it is shorter and consequently the shoulderI4 is closer to the open end l2. The block 6| has a central opening .62which merges-into a counterbored portion 64 defining .a flange 12extending 'inwardly of the tube 30. A threaded stem 66 having a head 68which serves as a circuit terminal extends through the opening 62 andthe head 68 fits snugly into the counterbored portion 64 and itsshoulder abuts against the block Si in the bottom of the counterboredportion 64. Nuts stem in place, to provide a fastening for a flexibleconductor (not shown), and to expand the block 6! and thereby assist inmaking a gas tight seal after mercury has been placed in the tube.

A suitable breaker 10 is secured against the edge of the flange 12. Aneccentric opening 14 through the breaker 'lll opens into a chamber 16between the head 68 and the breaker 10 in which the pool 4| of mercuryis retained. Due to the eccentricity of the opening 14, the chamber 34has a variable effective volume depending upon the rotated position ofthe tube 60. If the switch is in the position shown in Fig. 8, theeiiective volume of the chamber 34 is indicated by the dotted line 11 ofFig. 9. If the tube 60 is rotated 180 degrees, the effective volume ofthe chamber 34 is indicated by the dotted line 18 of Fig. 10.Intermediate values 'of effective volume are obtained if the tube 60 isrotated less than 180 degrees.

The valve mechanism 15 of the embodiments of Figs. 8 to 10 may bearranged as shown in Fig. 1 or as shown in Fig. 5 depending upon whethertime delay action is required in the opening or in the closing of acircuitthrough the switch. If a time delay in both opening and closingof the circuits through any of the described switches is desired, theseptum can be made rigid or two reversed septa can be utilized.

I claim:

1. An adjustable time delay, mercury flow switch comprising an envelopehaving two chambers from eachof which mercury can flow into the other, aquantity of mercury therein for rendering the switch operative to openand close a circuit through the switch upon predetermined distributionof the mercury in said chambers, means operatively interposed betweenthe chambers and having an axis normally disposed at an angle to thevertical and operative to vary the rate of flow of mercury from one ofsaid chambers into the other dependent upon the position to which saidmeans is rotated about its axis, said means and envelope being securedfor rotation together about said axis, whereby control of the mercuryflow may be obtained by rotation of the envelope about said axis, andmeans supporting the envelope for rotation about said axis.

2. In a mercury flow switch, the combination with an envelope having twosubstantially c0- axial aligned chambers from each of which mercury canflow into the other and a quantity of mercury in said envelope forrendering the switch operative to open and close a circuit uponpredetermined distribution of the mercury in said chambers, of meansoperable to permit retarded rate of flow of mercury from one of saidchambers into the other of said chambers at a rate. when the axis of thechambers is at an angle to an upright position, dependent upon theposition to which said envelope is rotated about said axis, and meanssupporting the envelope with said axis at an angle to the vertical.

3. An adjustable time delay mercury switch in which mercury flows fromone chamber to another-and the operation of the switch is dependent uponthe volume of mercury in one of the chambers and comprising a hollowbody containing mercury, a wall dividing the body into a pair ofsubstantially co-axial aligned chambers and having an orifice meanstherein which is eccentric with respect to said axis and of whichdifferent portions, circumferentially with respect to said axis, are ofdifferent effective area with respect to each other, whereby the rate offlow of said mercury through said orifice means can be selected byrotation of the body about said axis when said axis is at an angle tothe vertical, and means for supporting said body for rotation about saidaxis.

4. An adjustable time delay mercury switch in which mercury flows fromone chamber to another and the operation of the switch is dependent uponthe volume-of mercury in one of the chambers and comprising a hollowbody' containing mercury, a wall dividing the body into a pair ofsubstantially co-axial aligned chambers and having an orifice meanstherein which has a diil'erent area exposed to the mercury for differentaxial rotated positions of said body, whereby the rate of flow of saidmercury through said orifice means can be selected by rotation of thebody about said axis when said axis is at an angle to the vertical, andmeans for supporting the body for rotation about said axis.

5. A switching mechanism comprising an envelope, a pair of circuitterminals associated with said envelope, said envelope having aninternal passage for mercury to flow to and from one of said terminals,9. quantity of mercury in said envelope adapted to complete an electriccircuit through said terminals, a flexible septum rigidly supported andextending transaxially of said passage and having its margin free tofiex, said septum having an orifice means for permitting retarded flowof mercury through the passage, an annular projection extending fromsaid envelope into said passage near the periphery of said septum,whereby pressure of the mercury on one side of said septum causesthemarginal area of said septum to engage said projection to prevent theflow of mercury around said septum and the pressure of the mercury onthe other side of said septum causes said septum to flex to permit flowof mercury around said so turn.

6. A switching mechanisinaccording claim characterized in that'saidorifice means is eccentric with respect to the axis of said passage andof which different portions circumferentially with respect to said axisare of different efiective area with respect to each other.

7. An adjustable time delay mercury flow switch comprising a hollow bodyhaving a pair of chambers and in which mercury flows from one chamber tothe other and operation of the switch is effected when the volume ofmercury in one of the chambers is equal to the effective volume of saidchamber, mercury in said chambers, one of said chambers having an axisdisposed at an angle to the vertical, said one of said chambers having adifferent effective volume at different rotated positions with respectto its said axis, whereby rotation of said body about said axis when theaxis is at an angle to an upright position changes the volume of mercuryrequired to effect operation.

8. A mercury switch comprising a hollow body having a pair ofcommunicating chambers and in which the flow of mercury between thechambers is necessary for operation, mercury in the chambers, means forretarding the fiow from one chamber to the other chamber, said switchbeing rendered operative upon the surface of the mercury inone chamberreaching operating level, one of said chambers having an axis angularlydisposed to the vertical, and means operative upon rotation of the lastmentioned chamber about said axis to change the amount of mercuryrequired to cause its surface to reach,

operating level.

9. An adjustable time delay mercury flow switch in which mercury flowsfrom one chamber to another and operation of the switch is effected whenthe volume of mercury in one of the chambers is equal to the effectivevolume of said chamber and comprising a hollow body containing mercury,a wall dividing the body into a pair of chambers, one of said chambershaving an axis at an angle to the vertical and having a differenteffective volume at different axial rotated positions, whereby'rotationof said one chamber about its said axis when the axis is at an angle toan upright position changes the volume of mercury required to efiectoperation, said wall having an axis in fixed angular relation to theaxis of the chamber, and orifice means in said wall permitting retardedflow of mercury between said chambers at a rate dependent upon therot'ated'position of the wall about its axis when its axis is at anangle to an upright position.

10. An adjustable time delay mercury switch in which mercury fiows fromone chamber to another and the operation of the switch is dependent upona predetermined volume of mercury being in one of the chambers andcomprising a hollow body containing mercury, a wall dividing the bodyinto a pair of substantially co-axial aligned chambers and having anorifice means therein which is eccentric with respect to said axis andof which different portions, circumferentially with'respectto said axis,are of difiei'ent effective area with respect to each a other, wherebythe rate of flow of said mercury through said orifice means can beselected by rotation of the body about said axis when said axis is atangle to the vertical, and means operative upon rotation of the bodyabout said axis for predetermining said volume of mercury required foroperation.

11. A mercury flow switch combination according to claim 2 characterizedin that the combination includes a pair of circuit terminals associatedwith said envelope, said mercury being adapted to ailect the electricalconduction of a circuit through said terminals upon occurrence of apredetermined relative volume of said mercury in one of said chambers,and a means, operative consequent upon axial rotation of said envelope,for varying said predetermined volume.

12. In a mercury flow switch, a hollow body having a longitudinal axis,a valve member dividing the envelope into two aligned co-axial chambers,a quantity of mercury in one of said chambers, said valve member beingoperable to permit retarded flow of said mercury from said one chamberto said other chamber when said axis is at an angle to an uprightposition, a

pair of spaced circuit terminals, the level of the surface of themercury in said other chamber relative to one of said terminalscontrolling an electric circuit through said circuit terminals, meansoperative upon rotation of said envelope about said longitudinal axis topredetermine the amount of mercury required to reach said level in saidone chamber, and said valve member being operative to permit retardedfiow of said fiuid at predetermined rates depending upon the axialrotated position of said envelope.

13. An adjustable time delay, mercury flow switch comprising an envelopehaving two chambers, a quantity of mercury therein for rendering theswitch operative to open and close a circuit through the switch uponpredetermined distribution of the mercury in said chambers, fiow varyingmeans operatively interposed between the chambers and having an axisnormally disposed at an angle to the vertical and operative to vary therate of flow of mercury from one of said chambers into the otherdependent upon the position to which said flow varying means is rotatedabout its axis, whereby control of the mercury flow may be obtained byrotation of the flow varying means about said axis, and means supportingsaid flow varying means for rotation about said axis.

14. In a mercury flowswitch, the combination with means having twochambers and a passage for fluid connecting the chambers, a quantity ofmercury therein, means to retard the flow of said mercury from one ofsaid chambers to the other, and means responsive to a predetermineddisposition of said mercury in at least one of said chambers forefl'ecting operation of the switch, of means dependent upon the axialrotated position of said first means to change said predetermineddisposition of mercury required for efiecting operation.

15. An adjustable time delay mercury switch comprising a hollow bodyadapted to contain mercury, a wall dividing the body into twosubstantially coaxially aligned chambers, said wall having a pluralityof different sized perforations constituting orifices eccentric to theaxis of alignment, said perforations being circumferentially spacedabout said axis and located near the peripheral wall of said hollowbody, said switch being operable to efiect'different degrees of timedelay by flow of mercury from one chamadapted to contain mercury and inwhich mercury flows from one chamber to the other and operation of theswitch is efiected when the volume of mercury in one of the chambers isequal to the effective volume of that chamber, one of the chambershaving an axis disposed at an angle to the vertical and having abounding Wall intersecting said axis at an oblique angle wherebyrotation of said body about said axis when the said axis is at an angleto an upright position changes the volume of mercury required to effectoperation.

17. A mercury switch comprising a hollow body adapted to containmercury, said body having a pair of communicating chambers, said switchbeing rendered operable by flow of mercury from one chamber to the otherand in accordance with the mercury surface level reached in one of thechambers, means for retarding the flow from one chamber to the otherchamber, one of said chambers having an axis angularly disposed to thevertical and having an operating portion which is eccentric with respectto said axis and operative upon rotation of the last mentioned chamberabout said axis to change the amount of mercury required to cause itssurface to reach operating level.

. MILTON W. GRIFFES.

